This invention relates to a titanium member and more particularly it relates to titanium members formed from titanium powders, and more particularly, it relates to titanium alloy members such as internal combustion engine connecting rods and caps therefor. Further, the invention relates to the production of connecting rods having split bearing assemblies and matched mating surfaces at the large bore or circumferential opposite ends.
Connecting rods have three parts, namely, a small end or terminal portion with a small bearing hole, a large end with a large bearing opening and a rod portion connecting the small bearing to the large bearing. Most connecting rods are comprised of two members including a semi-circular end cap which forms approximately half the large bearing opening. The end cap is fastened to a mating surface formed as part of the connecting rod. The small end is an integral part of the connecting rod. The end cap is required to fit the connecting rod to the crank of the internal combustion engine. For some applications, the large end is comprised of an integrally formed large bearing opening similar to the small end.
Conventionally, the connecting rod was fabricated in two parts comprised of the end cap and connecting rod. However, considerable difficulty was experienced in precisely mating the end cap to the connecting rod to form the large bearing opening. To overcome the problem of matching the end cap to the mating surface, the end cap is forged against or cracked from the large bearing surface utilizing crack initiating indents to promote a cracking plane to provide an exactly remateable end cap surface. For example, U.S. Pat. No. 5,566,449 discloses a connecting rod as a shaft clamping member and includes a rod member and cap, each of which has mating faces at circumferentially opposite ends of a semi-circular recess and which are fastened to each other by bolts by matching the opposed mating faces to each other to define a crank pin hole by the two semi-circular recesses. The rod member and the cap are forgings formed from a titanium alloy and simultaneously produced by forging powder preforms of the rod member and cap in a cavity having the desired shape of the connecting rod. After forging, the opposed mating faces have an infinite number of recesses and projections which are formed from the flow of the material during the forging and which are in a matched and fitted relation to each other.
U.S. Pat. Nos. 5,353,500; 5,131,577; 5,109,605; 5,105,538; 4,993,134 and 4,936,163 disclose a method of making a connecting rod for attachment to a bearing journal by separation of parts of the connecting rod, including: (a) forging a powder metal sintered preform to provide a one-piece connecting rod having an annular wall defining a crank opening with a center axis and with stress risers for establishing a cracking plane that extends across the crank opening; (b) providing access for a compression coupling across the cracking plane; (c) while at ambient conditions, applying tension substantially uniformly across the cracking plane to propogate fracture from the stress risers along the cracking plane and thereby separate the connecting rod into a cap and body with cracked surfaces; and (d) remating the cap and body by applying a compression coupling through the access to draw the cap and body together under guidance and with metal yielding pressure to effect substantially an exact rematch of the cracked surfaces. Control of the diametrical clearance between the bolt shanks and the bolt openings, of the bolts used as the compression coupling, promotes guidance needed to achieve such rematch. The cracking is effected in an improved manner by use of continuous pulling apart of the rod in a direction perpendicular to the cracking plane.
U.S. Pat. No. 4,860,419 discloses a method for making split bearing connecting rods, including steps wherein previously clamped body and cap portions are quickly forced apart longitudinally to cause fracture separation of both pairs of integral legs in a single motion while the cap and body are restrained from substantial relative rotation by a clamp of a fracture separation apparatus.
U.S. Pat. No. 4,569,109 discloses split bearing assemblies having separable bearing caps for both single applications, such as connecting rods, and multiple applications, such as engine crankshaft supports, together with methods and apparatus for making such assemblies by integrally forming the caps with the main body and separating them by fracture separation. A two step separation method is disclosed with bore starter notches and semicircular die expanders that minimize split plane and bore distortion.
U.S. Pat. No. 5,051,232 discloses that the separation of two or more forged powder metal components is facilitated by forming a compacted and sintered powder metal preform with at least one slit that separates the component pieces. An anti-bonding agent such as graphite is introduced into the slit and the preform is then forged to final shape. The anti-bonding agent prevents the complete bonding of the powder metal pieces to each other thereby facilitating separation of the pieces at the slit. This method is particularly suited for the manufacture of piston connecting rod assemblies of the type including a connecting rod and cap.
U.S. Pat. No. 5,722,036 discloses a manufacturing process of a sintered connecting rod assembly comprising a first member with a projection and a second member with a concavity in which the first member and the second member are mated with each other by engaging the projection with the concavity. A powdered raw material is compacted into a first compact and a second compact for the first and second members, wherein the projection of the first compact has a width slightly larger than the width of the concavity of the second compact. Then the projection of the first compact is engaged with the concavity of the second compact to mate the first compact with the second compact, thereby the projection and the concavity are tightly pressed against each other. After sintering the mated first and second compacts, they are forced to release the projection from the concavity. The die for compacting the raw material has a whole cavity and a removable core for dividing the whole cavity into two cavities.
U.S. Pat. No. 3,994,054 discloses that the crankshaft bearing cap of a connecting rod is formed from a forged rod blank which includes an integral circular head having an internal bearing surface and have integrally formed interconnecting lug portions. The lug portions are provided with cracking openings aligned with and parallel to a cracking plane. Each of the openings is provided with a cracking notch or recess which extends downwardly from one side of the head between twenty and fifty percent of the opening length. The assembly is located on a lubricated supporting bed with the unnotched face resting on the supporting surface. Interconnected cracking pins with a suitable tapered configuration are simultaneously forced into the cracking holes with an impact type force. The tapered pins are interconnected to a common support equalizing the cracking impact pressure as the pins are moved into cracking openings. Each of the notches is formed with a V-shape with an inclusive angle of forty-five degrees and a relatively shallow depth of from 0.010 to 0.020 inches to define a sharp apex in the cracking plane. Suitably sized and circumferentially spaced radial lubrication holes in the cap provide improved lubrication and simplify the manufacturing process. The lubrication holes are spaced in accordance with the spacing of the needle roller bearings such that only one roller bearing is in aligned overlying relationship with each lubrication hole at any given instant.
U.S. Pat. No. 4,693,139 discloses that the bearing half and bearing cap are integrally connected together by bolts, chamfers are made in the peripheral portions of the bearing half and the bearing cap facing their broken and divided surfaces. Such chamfers are made before the dividing of the larger diameter end portion and thus cause the breaking and dividing operation to be facilitated.
U.S. Pat. No. 4,836,044 discloses that a multi-piece connecting rod has the large eye end formed with a yoke receiving a bearing bracket supported on an angled wedge surface by an angled counter surface of a wedge. The wedge is carried by a pin-like bolt between legs of the yoke and includes a threaded portion engaged by the bolt for tightening the angled wedge surfaces to clamp the bearing bracket in position.
U.S. Pat. No. 5,594,187 discloses an apertured connecting rod having a stress riser crease formed in one side thrust surface made by forging a powder metal sintered preform with a V-shaped notch mold formed in a side face whereby the spaced surfaces defining the V-shaped notch are folded inwardly toward one another during forging to create a deep crease without any substantial width.
In spite of these disclosures, there is still a great need for a titanium alloy based connecting rod having improved properties and fractured mating surfaces to provide exactly remateable end cap surfaces which can be fastened to form the large bearing opening in the connecting rod.